The present invention relates to slide gate plates and to the method of increasing the service life of burned alumina refractory slide gate plates which have been tar impregnated and baked.
Slide gate assemblies are well known devices utilized with metal working vessels and usually comprise at least one stationary refractory plate with a passage therethrough and at least one sliding refractory plate with a passage therethrough suitably engaged with the stationary plate. The sliding refractory plate is moved by suitable means in order to align the respective passages to permit discharge of molten metal from the metal working vessel. One of the major problems with such plates is that the portions thereof that are exposed to the molten metal are very susceptible to wear. Efforts to increase their wear resistance and, hence, the service life of the slide gate plates has been an ongoing concern. The high temperature and corrosive action of the molten metal passing through the passages in the slide gate plates tends to limit their service life.
A number of different types of refractory materials, including those based on magnesite and alumina, have been utilized as the refractory for such gates and it has been found that under most conditions the most suitable refractories are the alumina based refractories. In an effort to increase the wear resistance, both burned and unburned alumina refractories, which have also been tar impregnated and baked have been utilized and it has been found that most suitably the refractory slide gate plate once formed is preferably impregnated with tar. While such tar impregnated plates are superior to unimpregnated high alumina slide gates, further improvements in service life are desired.
One of the problems noted is that under the high temperature conditions to which the slide gates are employed there is rapid oxidation of the carbon derived from tar or pitch used to impregnate the plate, and this oxidation shortens the service life of the slide gate plate.